Testing Voltage drop using circuit impedance

[TonyM58]

Ok guys

got my head in the 17th edition

New bit in Part 6 Inspection and testing (used to part 7 in 16th)

612.14 - "the voltage drop may be evaluated by measuring the circuit impedance"

managed to find the same query on another forum, and lots of views on there about how you would actually do it (most of which, to be honest were very theoretical) and not 'set your meter to this, and measure that' type answers

What I need is a simple procedure as to how this would be done - naturally the regs dont actually telly you!!!!!

And please dont say'just work it out using mV/A/M'

Been there and (on occasion) done that

This is something new and i would be interested on how you guys think it can be achieved

 

[Cirrus]

Sorry to hijack Tony - get me pm and email last night?

 

[Bane]

Yeah, that'd work cirrus

 

[Cirrus]

WHAT?

 

[TonyM58]

Cirrus

yeah had a look earlier, emailed you back

Not good news i'm afraid.......

anyway, these v.drops using impedance..... c'mon guys.......

 

[Bane]

*Drums his fingers*

"Yeah, come on guys"

(Sorry, I'm bored. Going to sign off for the night methinks. Laters)

 

[MacSparky]

Ok Tony i'll give it a bash, not sure if im on the right track with this but here goes...

lb x R1+Rn / Ca Ci Cg Cr (factoring where appropiate) = Vd

This is new to me so apologies if ive just embarrased myself....lol... let me know what you think.
Regards,
MacSparky

 

[TonyM58]

Mac,

yeah thats pretty much what i thought,

but applying that practically is more complicated.

If you mearsure R1+Rn at the extremity of the circuit, you will also be including the external Z of the cirucuit.

So possibly, measure incoming Z (no load) Line to neutral. Measure Z at extremity, take this from incoming Z, will give you R1+Rn, although impedance rather than resistance.

if you multiply this by Ib, you get 'design' voltage drop. Alternatively if you multiply it by In, you get MAXIMUM voltage drop. plus your correction factors)

It seems a bit simplistic, but say if a radial circuit was designed to supply, say, a 2Kw load. If you was to measure Uo (or is it UoSTC now?) at incoming, then measure V at the load with load pulling design current, then, then that difference in voltage would be, basically the voltage drop.

The book says you dont need to verify this on initial verification, but on PIR's......

 

[MacSparky]

Well thats cheered me up...nice to see i was on the right track, bring on the year 2 exams lol...
Btw...had my year 2 practical assessment yesterday....think it went ok

 

[TonyM58]

Mac,

if you put an answer like that as a year 2 student.........

then good on ya,!!! i have spent many years in college, fairly high level, but i was stumped for a while

 

[MacSparky]

Must learn, more studying, need to know more lol
Thanks for the comment
Regards
MacSparky

 

[LukeScotty]

yep me too, just bought these ebooks, any one got them? what you think to them?

book 1
Electrical Installation Calculations Vol 1 & 2 on eBay, also Engineering, Science, Educational Textbooks, Books, Comics Magazines (end time 06-Mar-08 14:07:57 GMT)

book 2
Electrical Principles & Technology on eBay, also Engineering, Science, Educational Textbooks, Books, Comics Magazines (end time 09-Mar-08 17:50:01 GMT)

£1.99 each, e book

 

[MacSparky]

I have these books, purchased them from amazon about 3 months ago and paid about £17 for both vol's-(book 1) as above, copyright springs to mind LScotty...people like that grate on me